Suspended particulate matter in Southern ocean: An approach to understand source and processes

Abstract

The Southern Ocean, also known as Antarctic Ocean or the South Polar Ocean is the fourth largest of the world's five oceans. It encompasses roughly 20.3 million sq. km (7.8 million sq m) in area. Geologically the Southern Ocean is the youngest of the world's oceans. It formed around 30 million years ago when Antarctica and South America moved apart. It has several seas, the most oceanographically distinctive of which are the Ross and Weddell seas. It is considered as a crucial area in the contemporary cycle of matter. Two major sources responsible for supply of particles to the ocean are biogenic particles formed as a result of planktonic metabolism and Lithogenic particles, mostly clay and rock detritus, transported from continents by rivers, coastal erosion and wind. Also, as a result of resuspension of sediments, a large volume of lithogenic particles is transferred within the interior of the ocean. The mass concentrations of suspended particulate matter (SPM) in the ocean vary in different regions and at different depths due to various biotic and abiotic factors and depend on the geographical location, its productivity and the dynamics of its water masses. The knowledge on the distribution of SPM is an important prerequisite for the description and prediction of the ecological conditions. The SPM in the water column regulates the penetration depth of light and therefore it is an important parameter influencing primary productivity. Suspended barite is being used as a tracer of biological activity in Southern Ocean. Elemental chemistry of SPM will help us in understanding source of matter. The fundamental physical and chemical properties of water will vary depending on the type and origin of SPM. So far India through NCAOR of MoES, launched four expeditions in the Indian sector of the Southern Ocean during January - March 2004, January - April 2006, January - April 2009 and January - March 2010 and fifth one is presently on for January - April 2011. We from the Department of Marine Sciences of Goa University are part of all the expeditions except for the first one. Our studies on SPM and its chemistry have given interesting results. The observed variations in SPM were attributed to changes in productivity and/or to the difference in source of matter. In order to understand climatic changes through the study of Southern Ocean continuous and long term monitoring is essential. It is therefore proposed to be part of future Southern Ocean expeditions. We also propose to collect sediment cores to support our studies on past climate changes.